The paper presents the results of experimental determination of shear parameters at the contact between structures and foundation soil. In particular, the conducted research experimentally determined the ultimate shear resistance for a series of micropiles. The test scheme of the experimental samples was chosen so that, on the one hand, the main features of the stress state of the prototype were reproduced, and on the other hand, excessive difficulties in interpreting the experimental results were avoided. The most common and perhaps the most successful method involves testing by pulling the pile out of the soil. Based on the experimental results, the values of the maximum uplift forces (ultimate shear resistance), the stiffness characteristics of the interface element in the longitudinal direction (along the axis of the structure), and the stiffness characteristics of the interface element in the normal direction (perpendicular to the axis of the structure) were established. During the tests, it was assumed that the uplift force is a random variable and a single experiment is insufficient for its complete description. To ensure reliability, the data obtained in the tests were subjected to statistical processing. To eliminate random variations, six tests were carried out for each sample. The obtained results for the uplift forces completely contradict the design provisions of the current regulatory documents. The authors assume that the discrepancy between the provisions of the standards and the test results is caused by the neglect of the behavior of the contact layer.